Method and apparatus for adapting a propeller and shaft system

ABSTRACT

Method and apparatus for adapting a propeller system including a propeller shaft ( 15, 16 ) and a propeller ( 7, 8 ) adapted to be mounted on the propeller shaft ( 15, 16 ). The propeller system includes a propeller ( 7, 8 ) connected in a rotationally fixed manner to a propeller shaft ( 15, 16 ), the propeller shaft ( 15, 16 ) having a portion provided with splines ( 19, 20 ) which cooperate with corresponding splines ( 25, 28 ) inside the hub ( 23, 26 ) of the propeller ( 7, 8 ) in order to obtain the rotationally fixed connection, where the splines ( 19, 20 ) on the propeller shaft ( 15, 16 ) and in the hub ( 23, 26 ) of the propeller ( 7, 8 ) are helical, with a predetermined oblique angle (alpha, beta). The invention also relates to a propeller shaft ( 15, 16 ) and a propeller ( 7, 8 ) which are intended to be used in the propeller system.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims priority to Swedish PatentApplication No. 0200581-7 filed Feb. 27, 2002. Said application isexpressly incorporated herein by reference in its entirety.

BACKGROUND OF INVENTION

[0002] 1. Technical Field

[0003] The present invention relates to a propeller shaft adapted to beconnected to the output shaft of a drive motor, the propeller shafthaving a portion provided with splines in order to permit a rotationallyfixed connection to corresponding splines inside the hub of a propeller.

[0004] The invention also relates to a propeller including a hub withpropeller blades secured to the hub, which hub is provided with an axialthrough-opening in which splines are arranged in order to permit arotationally fixed connection between the propeller and a propellershaft with corresponding splines.

[0005] The invention additionally relates to a propeller systemincluding at least one propeller connected in a rotationally fixedmanner to a propeller shaft, the propeller shaft having a portionprovided with splines which cooperate with corresponding splines insidethe hub of the propeller in order to obtain the rotationally fixedconnection.

[0006] Still further, the invention relates to an adapter that enables apropeller system as described hereinabove regarding a propellerconnected in a rotationally fixed manner to a propeller shaft by way ofcooperating splines.

[0007] 2. Background Art

[0008] Propellers of the abovementioned type, for example on boats, aredriven by a drive motor. The torque delivered by the drive motor istransmitted to the propeller via a drive shaft leading from the motor, atransmission mechanism and a propeller shaft. Since the propeller isdesigned with a through-opening in the hub of the propeller, withsplines arranged in the through-opening, and the propeller shaft isdesigned with corresponding splines, a rotationally fixed connection isobtained, the two are joined together, so that the torque delivered bythe drive motor is transmitted to the propeller.

[0009] When the propeller of a boat is caused to rotate with the aid ofthe drive motor, the propeller generates a compressive force whichdrives the boat forward or backward depending on the direction ofrotation of the propeller. The compressive force gives rise to areaction force which is transmitted to the propeller shaft via thepropeller hub. The propeller shaft is therefore provided with a flangeagainst which the hub bears in order to take up the compressive forcewhen the propeller drives the boat forward, and an end nut against whichthe hub bears in order to take up the compressive force when thepropeller drives the boat backward.

[0010] A problem with the abovementioned type of spline connectionbetween the propeller hub and the propeller shaft is, however, that onlythe torque delivered by drive motor can be transmitted via the splineconnection. Consequently, the resulting compressive force is transmittedcompletely via the flange or end nut, which means that these have to begiven a relatively robust and therefore bulky construction, particularlyin the case of high-power motors. Another problem is that the propellerhub has to be made particularly robust, and therefore bulky, at thoseparts which are intended to bear against the flange or end nut. This isparticularly problematic in what are known as twin-screw arrangements,that is to say two propellers rotating counter to one another on thesame longitudinal geometric axis, where one propeller is connected to apropeller shaft extending through a bore in the second propeller'spropeller shaft, and where a large number of components therefore haveto be accommodated within a very limited space.

SUMMARY OF INVENTION

[0011] It is an objective of the present invention to provide apropeller shaft adapted to be connected to the output shaft of a drivemotor, where the rotationally fixed connection between propeller andpropeller shaft is arranged to at least partially take up thecompressive force which is transmitted to the propeller shaft, via thepropeller hub, of the propeller.

[0012] The invention thus relates to a propeller shaft adapted to beconnected to the output shaft of a drive motor, the propeller shafthaving a portion provided with splines in order to permit a rotationallyfixed connection with corresponding splines inside the hub of apropeller. The splines on the propeller shaft are in this case helical,with a predetermined oblique angle, and the axial compressive forceswhich are generated by the propeller are at least partially taken up bythe splines. This means that the axial limit stops, namely the flangeand the end nut, can have a simpler design.

[0013] A further objective of the present invention is to adapt theoblique angle so that the resultant between the tangential forcecomponent of the torque delivered by the drive motor and the propellingcompressive force is taken up in a direction substantially at rightangles to the splines. This means that the dimensions of the axial limitstops, namely the flange and the end nut, can be made smaller and thatthe propeller shaft can have the optimum strength.

[0014] By virtue of the fact that the direction of the helical shape ofthe splines along the circumferential surface of the propeller shaft,from the rear as viewed in the direction of travel, is chosencounterclockwise, with one propeller rotating counterclockwise andconversely one propeller rotating clockwise, the stresses on the axiallimit stops, namely the flange and the end nut, are reduced.Consequently, the stresses on the support surfaces of the propeller hubbearing against the limit stops are also reduced.

[0015] It is a further object of the present invention to make availablea propeller comprising a hub with propeller blades secured to the hub,which hub is provided with an axial through-opening in which splines arearranged in order to permit a rotationally fixed connection between thepropeller and a propeller shaft with corresponding splines. Therotationally fixed connection is arranged to at least partially take upthe compressive force which is transmitted to the propeller shaft, viathe propeller hub, of the propeller.

[0016] Thus, the invention also relates to a propeller comprising a hubwith propeller blades secured to the hub, which hub is provided with anaxial through-opening in which splines are arranged in order to permit arotationally fixed connection between the propeller and a propellershaft with corresponding splines. The splines in the hub are in thiscase helical with a predetermined oblique angle, and the axialcompressive forces which are generated by the propeller are at leastpartially taken up by the splines. This means that the support surfaceswhich are arranged on the hub of the propeller, and which are intendedto bear against the flange and the end nut, can have a simpler design.

[0017] According to a preferred embodiment of the propeller according tothe invention, the oblique angle is adapted such that the resultantbetween the tangential force component of the torque delivered by thedrive motor and the propelling axial compressive force is taken up in adirection substantially at right angles to the splines. This means thatthe size of the support surfaces on the hub of the propeller can bereduced and that the hub can have the optimum strength.

[0018] By virtue of the fact that the direction of the helical shape ofthe splines in the propeller hub, from the rear as viewed in thedirection of travel, is counterclockwise, with one propeller intended torotate counterclockwise during travel in the direction of travel andconversely one propeller rotating clockwise. As a result, the stresseson the axial limit stops, namely the flange and the end nut, are reducedand, consequently, the stresses on the support surfaces of the propellerhub bearing against the limit stops are also reduced.

[0019] It is a further object of the present invention to make availablea propeller system comprising at least one propeller connected in arotationally fixed manner to a propeller shaft, the propeller shafthaving a portion provided with splines which cooperate withcorresponding splines inside the hub of the propeller in order to obtainthe rotationally fixed connection. The rotationally fixed connection isarranged to at least partially take up the compressive force which istransmitted to the propeller shaft, via the propeller hub, of thepropeller.

[0020] It is a further object of the present invention to make availablean adapter to be included in a propeller system having a propellercoupled via the adapter in a rotationally fixed manner to a propellershaft wherein the propeller shaft has at least a portion provided withsplines which cooperate with corresponding splines inside a hub portionof the adapter in order to obtain the rotationally fixed connection. Thesplines on at least the propeller shaft are arranged at an oblique anglewith respect to a longitudinal axis of the propeller shaft, and in apreferred embodiment are helically arranged.

[0021] Thus, the invention relates to a propulsion system comprising apropeller connected in a rotationally fixed manner to a propeller shaft,the propeller shaft having a portion provided with obliquely orientedsplines which cooperate with corresponding splines inside the hub of thepropeller, or a suitably arranged adapter, in order to obtain therotationally fixed connection. Preferably, the splines on at least thepropeller shaft are of helical configuration.

[0022] According to a preferred embodiment of the present invention, afirst propeller is connected in a rotationally fixed manner to an outerpropeller shaft. A second propeller is connected in a rotationally fixedmanner to an inner propeller shaft extending through the outer propellershaft. The propeller shafts are drivably connected to a drive motor.This creates the conditions for a higher degree of overall efficiency ofthe propeller system.

[0023] In one embodiment, the propeller(s) and shaft(s) are arrangedbehind the driving lower unit in a “pushing” configuration. In analternative embodiment, the propeller(s) and shaft(s) are arranged aheadof the driving lower unit in a “pulling” configuration.

[0024] Further preferred embodiments and advantages of the inventionwill become evident from the attached patent claims and from thedescription given below.

BRIEF DESCRIPTION OF DRAWINGS

[0025] The invention will be described below on the basis of preferredillustrative embodiments and with reference to the attached figures,where:

[0026]FIG. 1 is a diagrammatic representation, partly in cross section,of a drive unit according to the present invention attached to the sternof a boat, and with the propeller's arranged in and “pushing”configuration;

[0027]FIG. 2 is a diagrammatic side view, partly in cross section andpartly in cutaway, of a pair of propeller shafts arranged for counterrotation, each with splines that are helical, with a predeterminedoblique angle;

[0028]FIG. 3 is a diagrammatic side view, partly in cross section andpartly in cutaway, of a pair of propellers arranged for counterrotation, each having splines in the through-opening of the respectivehub, which splines are helical, with a predetermined oblique angle;

[0029]FIG. 4 is a diagrammatic side view, partly in cross section andpartly in cutaway, of a pair of propellers arranged for counterrotation, together with respective adapters associated with each of thepropellers for affecting the association of the propellers withpropeller shafts adapted as depicted in FIG. 2; and

[0030]FIG. 5 is a diagrammatic representation, partly in cross section,of a drive unit according to the present invention attached to the sternof a boat with the propeller's arranged in and “pulling” configuration.

DETAILED DESCRIPTION

[0031]FIG. 1 is a diagrammatic representation, partly in cross section,of a drive unit 1 for boats with an inboard motor 2 and with a boatpropeller unit 4 attached to the stern 3 of the boat. The boat propellerunit 4 includes a shield 5 which is screwed to the stern 3, and in whicha propeller rig 6 is articulated in order to permit pivoting of the rig6 on the one hand about a vertical shaft for steering the boat, and onthe other hand about a horizontal shaft for trimming and opening thepropeller rig 6.

[0032] The torque delivered by the drive motor 2 is transmitted to afirst propeller 7 and to a second propeller 8 via a horizontal driveshaft 11 which is mounted in the shield 5 and which is connected in arotationally fixed manner to the flywheel 9 of the motor and to thedrive joints 10 of the propeller rig 6.

[0033]FIG. 1 also shows how the abovementioned drive joints 10 areconnected in a rotationally fixed manner to an upper angle switch 12.The upper angle switch 12 is arranged in the propeller rig 6 and isconnected in a rotationally fixed manner, by way of a vertical driveshaft 13, to a lower angle switch 14 for driving two substantiallyhorizontal propeller shafts, namely an outer one 15 and an inner one 16,with which the first propeller 7 and the second propeller 8 areconnected in a rotationally fixed manner.

[0034]FIG. 2 shows, partially in cutaway and partially in cross section,an outer propeller shaft 15, and an inner propeller shaft 16 extendingthrough the latter. The outer propeller shaft 15 is provided with aflange 17 against which a propeller hub positioned on the shaft 15 isintended to bear in order to take up some of the compressive force F_(R)which arises when the propeller is driving a boat forward. When thepropeller rotates in the opposite direction, that is to say to drive theboat in reverse, the compressive force F_(R) is partially taken upinstead by an end nut 18 arranged at the end portion of the propellershaft 15.

[0035] By providing the propeller shaft 15 with splines 19 which areformed at the propeller shaft 15 with a predetermined oblique angle(alpha), defined as the angle between the splines 19 and thelongitudinal direction or axis of the propeller shaft 15, it is possibleto transmit the tangential force component F_(T) of the torque deliveredby the drive motor 2 and also the reaction force generated by thecompressive force F_(R) of the propeller. The oblique angle (alpha) isdetermined after calculating the expected tangential force componentF_(T) and compressive force F_(R) so that the force _(S) acting on thesplines 19 is taken up substantially at right angles to these. In theexample shown in FIG. 2, the splines 19 are shown for a propeller 7rotating counterclockwise, as viewed from the rear in the direction oftravel. This means that the flange 17 and the end nut 18 can have asimpler design and that the propeller shaft 15 can be made smaller whileretaining its strength.

[0036] The inner propeller shaft 16 is also provided with splines 20which are formed in the propeller shaft 16 with a predetermined obliqueangle (beta), defined as the angle between the splines 20 and thelongitudinal direction or axis of the propeller shaft 16. The differenceis that the splines 20 are turned (as threads on a bolt or screw) in theopposite direction in relation to the above-described splines 19because, in the example represented in FIG. 2, they are shown for apropeller 8 rotating clockwise, viewed from the rear in the direction oftravel. The oblique angle (beta) is chosen in the same way as describedabove so that the force acting on the splines 20 is taken upsubstantially at right angles to the splines 20. This means that theflange 21 and the end nut 22 can have a simpler design and that thepropeller shaft 16 can be made smaller, which is particularlyadvantageous as it extends through the outer propeller shaft 15.

[0037] The oblique angles (alpha) and (beta) are determined taking intoconsideration the torque delivered by the drive motor 2, preferably at amotor speed corresponding to an expected cruising speed, and transmittedto each of the propellers 7, 8. Moreover, the configuration of thepropellers 7, 8, for example their blade areas, blade pitch anddirection of rotation, would be taken into consideration in thedetermination. By virtue of the fact that the direction of the helicalshape of the splines 19, 20 along the propeller shafts 15, 16, from therear as viewed in the direction of travel, is chosen counterclockwise,with one propeller 7 rotating counterclockwise and conversely onepropeller 8 rotating clockwise, it is possible to reduce the stresses onthe axial limit stops 17, 18, 21, 22 and, consequently, to also reducethe stresses on those support surfaces (not shown) of the hub 23, 26 ofthe propellers 7, 8 which bear against the limit stops.

[0038] There follows an example of the calculation of the oblique angles(alpha), (beta) for a typical diesel motor. The diesel motor delivers atorque of 560 Nm at cruising speed. With a total transmission of 1:1.78between the output drive shaft 11 of the motor 2 and the propellershafts 15, 16, the propeller shaft torque is 996 Nm, which, dividedbetween the two propeller shafts 15, 16, gives 498 Nm per shaft. Thesplines 19 of the outer propeller shaft 15 are further assumed to bearranged on the radius 24 mm, which gives the tangential force componentF_(T)=20750 N, and the splines of the inner propeller shaft 16 areassumed to be arranged on the radius 13.5 mm, which gives the tangentialforce component F_(T)=36889 N. Finally, the propellers 7, 8 are assumedto give approximately 5500 N in axial compressive force F_(R) at thecruising speed. To ensure that the force F_(S) will act at right anglesto the splines 19, 20 of the two propeller shafts 15, 16, the obliqueangle (alpha) for the outer propeller shaft 15 must therefore bearctan(5500/20750)=14.8 degrees, and the oblique angle (beta) for theinner propeller shaft 16 must therefore be arctan(5500/36889)=8.5degrees.

[0039]FIG. 3 shows the propellers 7, 8, partly in cutaway and partly incross section. For the sake of clarity, only the propeller 7 isdescribed in detail, because the design of the propeller 8 isprincipally the same. Extending through the hub 23 of the propeller 7there is a through-opening 24 in which splines 25 are formed with thesame oblique angle (alpha) as on the propeller shaft 15 in order topermit coupling of the two, with a rotationally fixed connection beingobtained for transmitting the torque delivered by the drive motor. Theoblique angle (alpha) is defined here as the angle between the splines25 and the axis of symmetry of the opening 24.

[0040] The propeller 8 is also designed with a hub 26, through whichthere extends a through-opening 27. Splines 28 with the oblique angle(beta) are formed in the through-opening 27.

[0041]FIG. 4 shows propellers 40, 41, partly in cutaway and partly incross section, together with propeller adapters 30, 31. For the sake ofclarity, only the propeller 40 and the associated adapter 30 aredescribed in detail, because the design of the propeller 41 and itsassociated adapter 31 are principally the same. In this embodiment ofthe invention, the propellers 40, 41 are of traditional design whereinsplines (or spline-receiving grooves, as the case may be) are orientedsubstantially parallel to a longitudinal axis of the propellers 40, 41.By way of the adapters 30, 31, propellers 40, 41, which are ofconventional design, are made compatible to specially configuredpropeller shafts 15, 16 as described hereinabove.

[0042] Extending through a hub 33 of the propeller adapter 30 is athrough-opening 34 in which splines 35 (or spline receivers 35, as thecase may be) are formed with the same oblique angle (alpha) as thespline configuration on the propeller shaft 15. This correspondingconfiguration between the two spline arrangements permits coupling ofthe adapter 30 to the propeller shaft, with a rotationally fixedconnection being obtained for transmitting the torque delivered by thedrive motor. The oblique angle (alpha) is defined here as the anglebetween the splines 35 and the axis of symmetry of the opening 34. Inthe illustrated embodiment, the exterior of the adapter 30 is providedwith splines conventionally arranged for mating engagement withreceiving grooves in a traditionally configured propeller. Byconventional design, it is meant that this spline arrangement betweenthe adapter 30 and the associated propeller shaft is orientedsubstantially parallel to a longitudinal axis of the propeller 40 andshaft.

[0043] The propeller adapter 31 is also designed with a hub 36, throughwhich extends a through-opening 37. Splines 38 with the oblique angle(beta) are formed in the through-opening 37. As described above, splinesof conventional configuration are provided on an exterior surface of theadapter 31 for mating engagement with a similarly configured propellerhub.

[0044] The invention is not limited to the embodiments shown in thedrawings and described above, and instead it can be freely varied withinthe scope of the attached patent claims. For example, embodiments of thepresent invention contemplate that the boat propeller unit can beequipped with a single propeller shaft, as well as a single associatedpropeller and adapter in corresponding configurations. Each case, thatis individually considering a single propeller, a single propeller shaftand/or a single adapter having obliquely oriented splines in associationtherewith, is considered to constitute a protectable aspect of thepresent invention.

[0045] It should be further appreciated that splined connections havebeen described and claimed with respect to the presently disclosedinvention(s). As will be appreciated by those persons skilled in theart, such splined connections are configured to prevent relativerotation between the so-connected components, and may take the form,among others, of abutting raised ridges, tabs, flanges and the like.Such splined connections may also assume a tongue-in-groove typeconfiguration wherein one member of the connection comprises aprojection and the corresponding member comprises a receiver for thatprojection. In this case, either the tongue or the groove may constitutethe spline. What should be appreciated as being at least one objectivewith regard to the presently disclosed invention(s) is that these“splined” connective members are at least partially obliquely orientedwith respect to a long axis of the propeller and shaft configurationwith which they are, or will be related. It is because of this obliqueorientation that forces are able to be taken up therein, thereby atleast partially relieving the force or stress that would have beentraditionally experienced a conventionally configured receiving shoulderor end-nut from the propulsive force generated by a rotating propeller.

[0046] Still further, as shown in FIG. 1, the propellers 7, 8 are in atrailing position to the power unit thereby forming a propulsion systemoriented in a “pushing” configuration. With respect to the presentinvention, it is also contemplated that the propellers may be arrangedin a leading position with respect to the power unit, thereby forming apulling configuration as shown in FIG. 5. Therein, the drive unit 1 a ofan inboard motor 2 a is shown mounted in the stern 3 a of a boat andconnected to a boat propeller unit 4 a. The two counter-rotatingpropellers 7 a, 8 a are shown in a leading or “pulling” configurationgenerally pointing in the direction of travel of the carrying boat. Sucha pulling configuration described is described in greater detail inInternational Patent Application PCT/SE01,00193, published as WO01/56876 and designating the United States, and which is herebyexpressly incorporated by reference, in its entirety, for purposes ofdisclosure in the present application.

1. A propeller shaft arrangement adapted to be connected to an outputshaft (11) of a drive motor (2) for causing propulsion of a carryingvehicle in a travel direction, the propeller shaft arrangementcomprising: a propeller shaft (15) having at least a portion thereofprovided with a spline (19) adapted to achieve a rotationally fixedconnection with a corresponding spline located inside a hub of acorresponding propeller; and said spline (19) being oriented at anoblique angle (alpha) with respect to a longitudinal axis of saidpropeller shaft (15).
 2. The propeller shaft arrangement as recited inclaim 1, wherein said spline (19) is helically arranged on saidpropeller shaft (15).
 3. The propeller shaft arrangement as recited inclaim 1, wherein said spline (19) is one of a plurality of splines (19),each of said plurality of splines (19) being oriented at thepredetermined oblique angle (alpha) with respect to a longitudinal axisof said propeller shaft (15).
 4. The propeller shaft arrangement asrecited in claim 1, wherein said propeller shaft (15) is one of aplurality of propeller shafts (15, 16) having a common longitudinalaxis, and each of said plurality of propeller shafts (15, 16) having atleast one spline (19, 20) positioned thereupon and oriented at anoblique angle (alpha, beta) with respect to the longitudinal axis. 5.The propeller shaft arrangement as recited in claim 4, wherein each ofsaid at least one spline (19, 20) is helically arranged on therespective propeller shaft (15, 16).
 6. The propeller shaft arrangementas recited in claim 5, wherein each of said at least one helicallyarranged spline (19, 20) is turned in a same direction, as viewed fromthe rear with respect to a direction of travel of a carrying vehicle, anassociated propeller would rotate to propel said propeller shaftarrangement in the direction of travel.
 7. The propeller shaftarrangement as recited in claim 5, wherein said at least one spline (19,20) on each of said propeller shafts (15, 16) is oriented at a differentoblique angle (alpha, beta) with respect to the longitudinal axis ofsaid propeller shafts (15, 16).
 8. The propeller shaft arrangement asrecited in claim 7, wherein each of said oblique angles (alpha, beta),with respect to the longitudinal axis of said propeller shafts (15, 16),is oriented such that a resultant force (F_(S)) between a tangentialforce component (F_(T)) of drive-motor-induced torque and acorresponding driving compressive force (F_(R)) is oriented at asubstantially right angle to the respective receiving spline (19, 20) ofsaid resultant force (F_(S)) when drive-motor power is applied.
 9. Thepropeller shaft arrangement as recited in claim 7, wherein orientationsof said oblique angles (alpha, beta), as measured with respect to thelongitudinal axis of said propeller shafts (15, 16), are predeterminedbased on an expected cruising speed of a drive motor to be associatedtherewith on a carrying vehicle.
 10. A propeller arrangement having ahub (23) with a through-opening (24) and blades connected thereto, thepropeller arrangement being adapted to be connected, via a propellershaft (15) to an output shaft (11) of a drive motor (2) for causingpropulsion of a carrying vehicle in a travel direction, the propellerarrangement comprising: a propeller (7) having at least a portionthereof provided with a spline (25) adapted to achieve a rotationallyfixed connection with a corresponding spline located on a correspondingpropeller shaft; and said spline (25) being oriented at an oblique angle(alpha) with respect to a longitudinal axis of said propeller (7). 11.The propeller arrangement as recited in claim 10, wherein said spline(25) is helically arranged on said propeller (7).
 12. The propellerarrangement as recited in claim 10, wherein said spline (25) is one of aplurality of splines (25), each of said plurality of splines (25) beingoriented at the predetermined oblique angle (alpha) with respect to alongitudinal axis of said propeller (7).
 13. The propeller arrangementas recited in claim 10, wherein said propeller (7) is one of a pluralityof propellers (7, 8) having a common longitudinal axis, and each of saidplurality of propellers (7, 8) having at least one spline (25, 28)positioned thereupon and oriented at an oblique angle (alpha, beta) withrespect to the longitudinal axis.
 14. The propeller arrangement asrecited in claim 13, wherein each of said at least one spline (25, 28)is helically arranged on the respective propeller (7, 8).
 15. Thepropeller arrangement as recited in claim 14, wherein said at least onespline (25, 28) on each of said propellers (7, 8) is oriented at adifferent oblique angle (alpha, beta) with respect to the longitudinalaxis of said propellers (7, 8).
 16. The propeller arrangement as recitedin claim 15, wherein each of said oblique angles (alpha, beta), withrespect to the longitudinal axis of said propellers (7, 8), is orientedsuch that a resultant force (F_(S)) between a tangential force component(F_(T)) of drive-motor-induced torque and a corresponding drivingcompressive force (F_(R)) is oriented at a substantially right angle tothe respective receiving spline (25, 28) of said resultant force (F_(S))when drive-motor power is applied.
 17. The propeller arrangement asrecited in claim 15, wherein orientations of said oblique angles (alpha,beta), as measured with respect to the longitudinal axis of saidpropellers (7, 8), are predetermined based on an expected cruising speedof a drive motor to be associated therewith on a carrying vehicle. 18.An adaptive arrangement having a through-opening (34) in a hub (33)thereof and the adaptive arrangement being configured to beinterstitially positioned between a propeller (7) and a propeller shaft(15) which is coupled to an output shaft (11) of a drive motor (2) forcausing propulsion of a carrying vehicle in a travel direction, theadaptive arrangement comprising: an adapter (30) having athrough-opening (34) with at least a portion thereof provided with aspline (35), said spline (35) adapted to achieve a rotationally fixedconnection with a corresponding spline located on a correspondingpropeller shaft, and said spline (35) being oriented at an oblique angle(alpha) with respect to a longitudinal axis of said adapter (30); and anexterior of said adapter (30) being configured for rotationally fixedengagement with a corresponding propeller.
 19. The adaptive arrangementas recited in claim 18, wherein said spline (35) is helically arrangedon said adapter (30).
 20. The adaptive arrangement as recited in claim18, wherein said spline (35) is one of a plurality of splines (35), eachof said plurality of splines (35) being oriented at the predeterminedoblique angle (alpha) with respect to a longitudinal axis of saidadapter (30).
 21. The adaptive arrangement as recited in claim 18,wherein said adapter (30) is one of a plurality of adapters (30, 31)having a common longitudinal axis, and each of said plurality ofadapters (30, 31) having at least one spline (35, 38) positionedthereupon and oriented at an oblique angle (alpha, beta) with respect tothe longitudinal axis.
 22. The adaptive arrangement as recited in claim21, wherein each of said at least one spline (35, 38) is helicallyarranged on the respective adapter (30, 31).
 23. The adaptivearrangement as recited in claim 22, wherein said at least one spline(35, 38) on each of said adapters (30, 31) is oriented at a differentoblique angle (alpha, beta) with respect to the longitudinal axis ofsaid adapters (30, 31).
 24. The adaptive arrangement as recited in claim23, wherein each of said oblique angles (alpha, beta), with respect tothe longitudinal axis of said adapters (30, 31), is oriented such that aresultant force (F_(S)) between a tangential force component (F_(T)) ofdrive-motor-induced torque and a corresponding driving compressive force(F_(R)) is oriented at a substantially right angle to the respectivereceiving spline (35, 38) of said resultant force (F_(S)) whendrive-motor power is applied.
 25. The adaptive arrangement as recited inclaim 23, wherein orientations of said oblique angles (alpha, beta), asmeasured with respect to the longitudinal axis of said adapters (30,31), are predetermined based on an expected cruising speed of a drivemotor to be associated therewith on a carrying vehicle.
 26. A propulsionarrangement adapted to be connected to an output shaft (11) of a drivemotor (2) for causing propulsion on a carrying vehicle in a traveldirection, the propulsion arrangement comprising: a propeller (7) havingat least a portion thereof provided with a spline (25) adapted toachieve a rotationally fixed connection with a corresponding spline (19)located on a corresponding propeller shaft (15), said spline (25) onsaid propeller (7) being oriented at an oblique angle (alpha) withrespect to a longitudinal axis of said propeller (7); and said propellershaft (15) having at least a portion thereof provided with said spline(19) adapted to achieve a rotationally fixed connection with thecorresponding spline (25) located inside the propeller (7), said spline(19) of said propeller shaft (15) being oriented at an oblique angle(alpha) with respect to a longitudinal axis of said propeller shaft(15).
 27. The propulsion arrangement as recited in claim 26, whereinsaid splines (19, 25) are helically arranged on said propeller shaft(15) and said propeller (7), respectively.
 28. The propulsionarrangement as recited in claim 26, further comprising: said propeller(7) being one of a plurality of propellers (7, 8) having a commonlongitudinal axis, and each of said plurality of propellers (7, 8)having at least one spline (25, 28) positioned thereupon and oriented atan oblique angle (alpha, beta) with respect to the longitudinal axis;said propeller shaft (15) being one of a plurality of propeller shafts(15, 16) having a common longitudinal axis, and each of said pluralityof propeller shafts (15, 16) having at least one spline (19, 20)positioned thereupon and oriented at an oblique angle (alpha, beta) withrespect to the longitudinal axis; and said splines (19, 20, 25, 28)being configured for mating engagement that fixes relative rotationalmovement between said propeller (7) and said propeller shaft (15) whendrive-motor power is applied.